A US size 7 crochet hook is 4.5 mm. It sits between the G-6 (4 mm) and the H-8 (5 mm), and it has no standard US letter, so brands stamp it with the number 7 and the 4.5 mm size instead.
Size 7 crochet hook in mm at a glance
| Millimeters | 4.5 mm |
|---|---|
| US size | 7 (no standard letter) |
| Smaller neighbor | G-6, 4 mm |
| Larger neighbor | H-8, 5 mm |
| Typical yarn | DK to light worsted (weights 3–4) |
Don’t mix up a size 7 with a 7 mm hook
The number on a size 7 crochet hook is a size label, not a measurement. A 7 mm hook is a much bigger tool, between a K-10.5 (6.5 mm) and an L-11 (8 mm), and it suits bulky yarn. If a pattern says “size 7” next to worsted or DK yarn, it means the 4.5 mm hook.
When “size 7” means a steel hook
Steel hooks for crochet thread use their own numbers, and they run backwards: the higher the number, the smaller the hook. A size 7 steel hook is about 1.65 mm on the Craft Yarn Council chart, and some brands label a 1.5 mm steel hook as 7. If the pattern calls for crochet thread, doilies or lace, a “size 7” is the steel hook, not the 4.5 mm one. Go by the mm number on the hook whenever you can.
Size 7 compared with nearby sizes
| US size | mm | Compared with a size 7 |
|---|---|---|
| G-6 | 4 mm | 0.5 mm smaller; tighter, firmer fabric |
| 7 | 4.5 mm | — |
| H-8 | 5 mm | 0.5 mm larger; looser, softer fabric |
The 4.5 mm half-step is handy when your gauge swatch comes out too tight on a G-6 but too loose on an H-8. For what to make with it and how it handles different yarns, see our full size 7 crochet hook guide.
Frequently asked questions
What mm is a size 7 crochet hook?
A US size 7 crochet hook is 4.5 mm. It sits between the G-6 (4 mm) and the H-8 (5 mm).
Is a size 7 crochet hook the same as a 7 mm hook?
No. A size 7 is 4.5 mm. A 7 mm hook is much larger, sits between the K-10.5 (6.5 mm) and the L-11 (8 mm), and is used for bulky yarn.
What size is a size 7 steel crochet hook?
About 1.65 mm on the Craft Yarn Council chart, though some brands label a 1.5 mm steel hook as 7. Steel hooks are used with crochet thread.
What yarn goes with a size 7 crochet hook?
DK to light worsted yarn (weights 3–4) is the usual match for a 4.5 mm hook.